Based on the information you supplied (which isn't much): 100 Document CALs.

If you want to avoid making the wrong decision, describe your user environment in full, or talk to your Qlik Partner.

A tip: Session CALs are expensive and a single one - if you choose to configure your server accordingly - allows anyone of the 7 billion inhabitants of this planet to access your document, but only one user at a time. However, you didn't say how many users are going to visit this document at the same time...

A DOC cal can only be shared if you respect the quarantine period of 24 hours. If a license has been unused for 24 hours you can re-assign it to another user, which mean the original user no longer has a license. Any attempt to circumvent the quarantine hours and/or impersonating users to allow sharing of a license would be a clear violation of the terms of use.